The cyclodextrin inclusion complexes of acylferrocenes: their preparation, and the induced Cotton effects in their circular dichroism spectra

Cyclodextrins as Supramolecular Hosts for Organometallic Complexes

“…β-CD and γ-CD formed 1:1 stoichiometric inclusion complexes whereas α-CD formed a 2:1 (CD−guest) complex with Fc. Even if other studies on complexes of α-, β-, and γ-CD with acylferrocenes (C 5 H 5 FeC 5 H 4 −COR, R = H, CH 3 , CF 3 ; XC 5 H 4 FeC 5 H 4 Y, X = Y = COCH 3 , X, Y = COCH 2 CH 2 , COCH 2 CO) showed that the signs of the Cotton effect exhibited no simple correlation with the proposed geometry, the orientation of Fc in the CD cavity was definitely confirmed by comparing the induced circular dichroism spectrum of a hindered Fc derivative (1,4,7,10,13-pentaoxa[13]ferrocenophane) for which an equatorial inclusion is only possible in the presence of β-CD with that of Fc in β-CD or γ-CD . Indeed, it has been unambiguously demonstrated that the orientation of Fc in β-CD is considered to be nearly parallel to the molecular axis of β-CD while that of Fc appears to be close to normal to the molecular axis of the γ-CD .…”

“…The second-sphere coordination adducts between native or chemically modified CD and Fc or its derivatives have been the subject of numerous studies using a wide range of techniques, among which induced circular dichroism was the first to establish the stoichiometry of the inclusion complexes. − Three structures were proposed for these adducts as shown in Figure . − The stoichiometry of the Fc−CD complexes was found to be dependent on the sizes of the CDs. β-CD and γ-CD formed 1:1 stoichiometric inclusion complexes whereas α-CD formed a 2:1 (CD−guest) complex with Fc.…”

Solvent- and Temperature-Tuned Orientation of Ferrocenyl Azide Inside β-Cyclodextrin

“…Ferrocene produces in ethylene glycol a positive ICD band for β-CyD and a small negative one for γ-CyD in the range of its d−d transition band of FcH. , Therefore, two different dominant orientations were proposed for FcH in β-CyD and in γ-CyD. The axial arrangement of ferrocene was attributed to β-CyD and the equatorial one to the FcH@γ-CyD complex …”